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ahaka

744X pole crossings

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Just wondering if this will be fully implemented in the 744X now that its possible to cross north and south poles in FSX? Cant wait to try some polar routing with the 747. :)

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Guest D17S

Get me an airplane and we'll just have to give it a try. I feel a test flight comin' on. "Wings Level Mode" within 10 miles of the pole? Right? . . . or was that the MD11? The rest, I think we already had pretty well nailed. Gonna miss that Polar Wall . . . not.

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Don't see any reason why it shouldn't work - that was a problem with FS9, not with the 744... it uses great circle calculations and we now have a real great circle in FSX right?


Ryan Maziarz
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This raises another question in my mind. At what point should you switch to TRUE north heading on ND? Do you wait or see as the readings get unreliable or is there a rule, like after crossing a certain latitude you switch into true heading mode?

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I remember somewhere there was something that told you when to switch but I can't find it anymore. I think it may have been in the iFly manual. (Sorry, pre-PMDG days.) Anyway, I wouldn't wait until the readings get unreliable. Even if you switch to TRUE, I found (the hard way as usual) that the track still becomes highly unreliable. I had to completely disable LNAV and switch to a HDG mode. I just flew a B-line strait through the Magnetic pole.Ryan GamurotLucky to live Hawai'ihttp://www.virtualpilots.org/signatures/vpa296.png


Ryan Gamurot
 

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Guest D17S

All the polar nav sequencing is entirely automated. There's a lot going on and it's real interesting to just sit back and watch the action. Gotta know what you're looking for, though. The only automated switchover we couldn't see was the actual pole crossing. The MD goes disengages all nav functions and goes into a "wings level" mode within a 20 mile radius of the pole. Not sure about the 744. There's a pole test-flight sequence back in the forum somewhere. PMDG did a pretty darn good job modeling these nav sequences. Looking forward to gettin' over the pole in a real airplane. Soon?

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>pole crossing. The MD goes disengages all nav functions and>goes into a "wings level" mode within a 20 mile radius of the>pole. Not sure about the 744. What happens in the 744 close to the Poles is fairly well described in the Boeing 744 manual. But just briefly (though details are more involved) a switch to True North reference occurs at about 82 deg. lat and it is annunciated to the pilot with some boxes flashing, etc. There is no mention of autopilot going into wings-level mode.Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg


Michael J.

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When I flew over the magnetic north pole, the aircraft said in LNAV mode. When the track started shifting, the plane would bank left and right to try and get back on track as it bounced from one place to another. Also, my instruments didn't automatically switch to TRUE headings. Is this modeled? Ryan GamurotLucky to live Hawai'ihttp://www.virtualpilots.org/signatures/vpa296.png


Ryan Gamurot
 

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Guest D17S

If I remember right the sequence is: 1) Auto reversion to True at some lat, then . . . 2) GPS present position updates to the FMS stop at a lat. This leaves the FMS's present position data provided by non-updated IRS Triple-mixed PP calculation, Both FMSs are now getting T-mixed PP data from the 3 IRSs . . . . then . . . 3) The number 3 IRU drops out and the 1 and 2 IRSs split. Each IRS (1 and 2) individually provides PP data only to its on-side FMS. This auto-sequence is modeled in the FS9 version, but with FS9 we never could get close enough to the pole to try the rest. 4) Finally, your Lnav experience might explain why (at least the MD) the AFDS kicks off ALL nav functions directly over the pole and reverts to a wings level mode. That would be the GGM (Guided Missile Mode).I really imagine the 744 has something similar. It's gotta. (But there on the other hand, its AFS is a full generation behind the MD11!)OK, now the manual quotes . . .

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Ryan isn't absolutely right here - there are still some issues with crossing the poles, particularly with the math involved behind it. We concentrated so much in getting the 747-400X into FSX shape that, as Phil Taylor loves to say, "we had to leave some features for the next version".As much as we would like to say that "it's 100% perfect", in this scenario, it's not. I hope that we'll gain your understanding by being perfectly honest and forthright about it and we definitely promise that we'll try to get it right as time progresses. The problem right now is that it's not "so simple" to make it perfect and we much prefer to not delay the release even further by choosing to deliver this feature in its entirety as well.Hopefully brutal honesty works ;-).


Lefteris Kalamaras - Founder

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Hi Lefteris and thank you for a straight and honest reply.May I ask though, what do you mean by it not being "100% perfect"? Does it mean that its not even worth trying to cross the poles, or just that there are some minor things that need to be adjusted? Can autopilot fly you over the pole? For now, I'd already be happy if its doable without a major headache. :)

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>Hi Lefteris and thank you for a straight and honest reply.>>May I ask though, what do you mean by it not being "100%>perfect"? Does it mean that its not even worth trying to cross>the poles, or just that there are some minor things that need>to be adjusted? Can autopilot fly you over the pole? For now,>I'd already be happy if its doable without a major headache.>:)Just before you cross the pole, switch to HDG HOLD and wait until you've crossed to go back to LNAV. That worked for me in FS9.Ryan GamurotLucky to live Hawai'ihttp://www.virtualpilots.org/signatures/vpa296.png


Ryan Gamurot
 

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How can it work for you in FS9? It is impossible to cross the pole there. At least for me the aircraft just stops moving forward like theres an invisible wall.Just to clarify: I'm talking about the true north pole, not the magnetic north pole which is somewhere in Canada.

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Guest D17S

Try it in the FS9 version. The FS9 Polar wall was about 20 miles from the pole. We can get there without any significant issue with the FS9 version. The only problem I saw was that the NDs didn't display IRU side -for-side PP updating. The NDs annunciated their FMSs were being provided PP by the #1 IRU. That was wrong, However the FMS's cdu properly annunciated split IRU ops. That was right. Hardly a big deal. The rest was there. If the FSX airplane can do At Least what the current FS9 airplane can do, there are No significant problems up to that last 20 miles. We might need to adjust our conception of what PMDG means when they say "100% perfect." Generally it means, "The car won't even run." With the PMDG group, it's more likely to mean, The darn thing still won't do the 1/4 mile in less than 6.2 seconds." 100% means it won't please me . . . but that's never gonna happen anyway! Start to learn about the pole navigation reversion sequence in the FS9 version. The level of detail the FS9 airplane's nav systems provides is Very good,but not absolutely 100%. Once you can even see the discrepancy, you'll be ready for the last 2% toward that stated 100% goal. The FSX version should only have that last 20 miles of additional functionality to deal with. Maybe it all fell apart there, but I doubt it. The real airplane has "math problems" with that last little bit too. Remember the wings level mode? That's the way Boeing dealt with it In Real Life.

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>How can it work for you in FS9? It is impossible to cross the>pole there. At least for me the aircraft just stops moving>forward like theres an invisible wall.>>Just to clarify: I'm talking about the true north pole, not>the magnetic north pole which is somewhere in Canada.I don't think there would be any NAV problems with the True North Pole. It's just the Magnetic North Pole because the IRU's can't figure out why they're pointing straight down and where they are. There also aren't any VHF stations for DME updating and GPS doesn't work (in real life) that far north.The limitation in FS9 was that there was no True North Pole. In FSX, it is there so you shouldn't 'hit the wall' any more.Ryan GamurotLucky to live Hawai'ihttp://www.virtualpilots.org/signatures/vpa296.png


Ryan Gamurot
 

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